Cartweaver dynamically determines how many options a product has, and displays the options in the most efficient way possible. If a product has only one option, then you get one select list. If a product has two options, and you've elected to use the Advanced Details Display type, then two dynamic select lists will be displayed, making it impossible for a user to pick an option that's not available. If a product has more than two options, then a table listing all of the available SKUs is displayed.